1. Field of the Invention
The invention relates to multi V-grooved sheet metal pulleys, and particularly to a new sheet metal multi V-grooved pulley structure having a plurality of pairs of roller spun coldworked groove-forming flange walls which form the V-grooves therebetween; and in which the metal thicknesses of the flange walls decrease progressively from the pulley hub flange wall.
The invention relates further to a new combination of steps by which such a multi V-grooved sheet metal pulley may be made to provide a series of groove-forming walls in a one piece cup-shaped sheet metal blank, in which the metal thickness of the groove-forming walls decrease progressively away from the hub wall.
2. Description of the Prior Art
Many procedures have been used and are known for the formation of V-grooved sheet metal pulleys from flat sheet metal discs. Many of these procedures involve stamping and drawing operations to produce at least the cup-shaped blanks from which the V-grooved pulleys are subsequently roller spun. Examples of such stamping and drawing operations are shown in U.S. Pat. Nos. 2,493,053 and 3,080,644.
Finished V-grooved pulleys or the cup-shaped stage blanks for subsequent spinning into V-grooved pulleys which are produced by such prior stamping and drawing methods are not balanced dynamically since the pulleys and blanks are formed by a series of progressive die steps on a non-rotating blank.
Many of these problems have been eliminated by the metal spinning procedure set forth in my copending application Ser. No. 584,388, filed June 6, 1975, in which a dynamically balanced cup-shaped metal blank is formed by roller spinning a disc against a headstock die, into which blank then is roller formed a plurality of pulley V-grooves. A cup-shaped stage blank produced by this method has a circular hub wall and a cylindrical cup wall with generally uniform metal thickness throughout the axial length. Subsequently, the flange walls forming the V-grooves which are in the cylindrical wall have equal thicknesses for each pulley groove.
In most equipment where such multi V-grooved pulley structures are used, the forces which are experienced by the individual V-grooves, decrease progressively along the cylindrical pulley wall in a direction away from the circular hub flange wall. Thus, the flanges which form the pulley groove immediately adjacent the hub wall experience greater stresses and forces than do the V-groove forming flanges which are located further axially along the cylindrical wall from the hub flange wall. Correspondingly, the outermost V-groove forming walls or flanges experience the least amount of force and stress thereon. Due to these conditions, the metal thicknesses or strength of the outer endmost pulley groove flanges need not be as great as the innermost pulley groove flanges. Therefore, most known pulley structures have more metal in the outer V-groove forming flanges than necessary, which increases the cost of the pulley.
Accordingly, there exists the need for a new multi V-grooved pulley structure and a method of making such a pulley which provides sufficient strength and rigidity to the groove forming flanges without excess metal being used in forming the outermost flanges.